1. Field of the Invention
This invention pertains to helically splined rotary actuators of the type of either a single helix or double helix. The invention pertains to the combination of such helical rotary actuators with linear actuators for combined linear and rotational movement. The invention also pertains to improvements in the helically splined rotary actuator in that a separately internally mounted ring gear is provided.
2. Description of the Prior Art
Helically splined rotary actuators have heretofore been provided with a ring gear having splines that mesh with a splined piston sleeve for converting linear motion of the piston within the actuator to rotary motion of an output shaft. Either the output shaft is held stationary and the outer housing is rotated or, more commonly, the outer housing is held stationary and the output shaft is rotated. The ring gear in these actuators has heretofore either been integrally formed as a part of the outer cylindrical body, with its splines machined into the integral part of the body, the ring gear has been welded rigid to the outer cylindrical body or the ring gear is held in a flange between two halves of the body.
In the first case of machining the ring gear as a part of the body, considerable machining time and skilled labor are required, making the actuator expensive to manufacture. Secondly, it is generally only possible to machine the splines integrally in the ring gear if the cylinder or cylindrical body is in two sections and the remainder of the outer cylindrical body is later joined as a separate section to the housing. An example of this type of helically splined rotary actuator is found in U.S. Pat. No. 4,373,426 Ser. No. 960,043, filed Nov. 13, 1978.
The other common way of connecting the ring gear is by bolting the ring gear separately to the outer cylindrical housing by a coupling flange which then holds together two separate sections of the outer cylindrical housing. An example of this type of ring gear is shown in U.S. Pat. No. 3,339,463. The mounting flange precludes the use of the actuator as a sliding member within an outer hollow boom or the like. Furthermore, the actuator is difficult to manufacture, requiring several separate parts, has little capability of handling bending moments on the actuator within normal size constraints and is difficult to seal against fluid leakage.
Combined linear and rotary actuators are known. These combined linear and rotary implements have been expensive to manufacture and unwieldy in use. Examples are shown in U.S. Pat. Nos. 4,029,165; 3,933,218; and 3,766,831.